On Sat, 24 Oct 2026, Aman Sharma <[email protected]> wrote: > When an HDMI connector is forced enabled (e.g. via video=HDMI-A-1:e for > laptop clamshell operation) and the external monitor enters DPMS standby, > some monitors (such as the BenQ GW2790Q) power down their internal DDC/I2C > controller, causing SCDC/EDID reads to fail with -ENXIO (-6). > > Currently, intel_hdmi_detect() and intel_hdmi_force() unconditionally call > intel_hdmi_unset_edid() before calling intel_hdmi_set_edid(). When > drm_edid_read_ddc() returns NULL during monitor standby, the connector's > cached detect_edid is wiped out and > drm_helper_probe_single_connector_modes() falls back to the 1024x768 VESA > no-EDID mode. When the monitor wakes back up, because the connector status > remained forced to connector_status_connected, no hotplug state transition > occurs and the display remains stuck at 1024x768 until a manual mode probe > (such as toggling the laptop lid) is triggered. > > Fix this by moving intel_hdmi_unset_edid() into intel_hdmi_set_edid() after > checking whether a forced-on connector (DRM_FORCE_ON or > DRM_FORCE_ON_DIGITAL) already has a valid cached EDID (detect_edid and > edid_blob_ptr) when DDC fails, and preserving connector_status_connected > on Gen11+ digital port disconnect when a forced-on connector has a cached > EDID. When the monitor is awake or a different monitor is plugged in, > drm_edid_read_ddc() succeeds, resets the previous EDID and dp_dual_mode > state via intel_hdmi_unset_edid(), and updates the connector with the new > EDID.
Connector forcing and EDID reading/caching need to remain orthogonal. The patch at hand makes a complex thing more complex. Please file a bug as described at [1], reproducing the problem. [1] https://drm.pages.freedesktop.org/intel-docs/how-to-file-i915-bugs.html > v3: > - Explicitly check for DRM_FORCE_ON / DRM_FORCE_ON_DIGITAL so DRM_FORCE_OFF > still clears the cached EDID as expected. > - Report connector_status_connected on Gen11+ disconnect when a forced-on > connector retains its cached EDID, and jump to out in > intel_hdmi_set_edid() so CEC physical address remains valid and > drm_helper_probe_detect_ctx() does not increment epoch_counter on > standby HPD pulses. > > v2: > - Move intel_hdmi_unset_edid() into intel_hdmi_set_edid() so hotplug > detection via intel_hdmi_detect() also preserves the cached EDID on > forced connectors and resets dp_dual_mode when updating EDID. > - Clear detect_edid on Gen11+ disconnect when the connector is unforced, > and verify edid_blob_ptr is non-NULL before retaining detect_edid. > > Signed-off-by: Aman Sharma <[email protected]> > --- > drivers/gpu/drm/i915/display/intel_hdmi.c | 31 ++++++++++++++++++----- > 1 file changed, 25 insertions(+), 6 deletions(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c > b/drivers/gpu/drm/i915/display/intel_hdmi.c > index b6fa1a1558b8..a14a857dfe94 100644 > --- a/drivers/gpu/drm/i915/display/intel_hdmi.c > +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c > @@ -2570,6 +2570,21 @@ intel_hdmi_set_edid(struct drm_connector *_connector) > intel_gmbus_force_bit(ddc, false); > } > > + /* > + * If the connector is forced on (e.g. video=HDMI-A-1:e) and the sink's > + * DDC/I2C bus is powered down during DPMS standby, keep the previously > + * cached EDID rather than wiping it and falling back to 1024x768. > + */ > + if (!drm_edid && > + (connector->base.force == DRM_FORCE_ON || > + connector->base.force == DRM_FORCE_ON_DIGITAL) && > + connector->detect_edid && connector->base.edid_blob_ptr) { Drivers also have no business looking at edid_blob_ptr. BR, Jani. > + connected = true; > + goto out; > + } > + > + intel_hdmi_unset_edid(&connector->base); > + > /* Below we depend on display info having been updated */ > drm_edid_connector_update(&connector->base, drm_edid); > > @@ -2580,6 +2595,7 @@ intel_hdmi_set_edid(struct drm_connector *_connector) > connected = true; > } > > +out: > intel_display_power_put(display, POWER_DOMAIN_GMBUS, wakeref); > > cec_notifier_set_phys_addr(intel_hdmi->cec_notifier, > @@ -2611,10 +2627,15 @@ intel_hdmi_detect(struct drm_connector *_connector, > bool force) > wakeref = intel_display_power_get(display, POWER_DOMAIN_GMBUS); > > if (DISPLAY_VER(display) >= 11 && > - !intel_digital_port_connected(encoder)) > + !intel_digital_port_connected(encoder)) { > + if ((connector->base.force == DRM_FORCE_ON || > + connector->base.force == DRM_FORCE_ON_DIGITAL) && > + connector->detect_edid && connector->base.edid_blob_ptr) > + status = connector_status_connected; > + else > + intel_hdmi_unset_edid(&connector->base); > goto out; > - > - intel_hdmi_unset_edid(&connector->base); > + } > > if (intel_hdmi_set_edid(&connector->base)) > status = connector_status_connected; > @@ -2638,10 +2659,10 @@ intel_hdmi_force(struct drm_connector *_connector) > if (!intel_display_driver_check_access(display)) > return; > > - intel_hdmi_unset_edid(&connector->base); > - > - if (connector->base.status != connector_status_connected) > + if (connector->base.status != connector_status_connected) { > + intel_hdmi_unset_edid(&connector->base); > return; > + } > > intel_hdmi_set_edid(&connector->base); > } -- Jani Nikula, Intel
